介孔铁基MOFs/纳米零价铁高效Fenton催化降解大分子污染物及反应机理

Heterogeneous Fenton process is particularly useful for cleaning high concentration and biologically toxic wastewater. How to carry out this reaction with high activity, low iron leaching and the possibility of employing the system at wide pH environments is still of special interest for environmental protection in the present time. This project first proposes to construct a novel and multiplicated heterogeneous Fenton system based on mesoporous iron metal-organic framework materials (mesoMOFs(Fe)).An important feature of mesoMOFs is that their framework structure, pore environment and functionality can be finely controlled by the choice of metal and organic building ligand and how they connected. These motivations thus spark the application of mesoMOFs(Fe)to heterogeneous Fenton system in order to improve the activity and stability of catalyst.Moreover, due to the tunable porosity and high surface areas of mesoMOFs(Fe), it would be favorable to design mesoMOFs(Fe) as a support to combining active iron nanoparticles(NPs) within pores and/or cavities. Both the reactivity and stability of iron NPs would be also enhanced in this way. The synergic effect generated between iron NPs and mesoMOFs pores can also promote catalytic reactivity. Additionally, iron-containing organic complex catalysts can eaily take Fenton oxidation at neutral pH. That is to say, we can carry out Fenton reaction under wide pH range by surface modifation of mesoMOFs(Fe)catalysts. Moreover, due to the enhanced adsorption properties of mesochannel and mesocages, this novel Fenton system would be potentially for the application in large-scale pollutant treatment with varied pH value, such as pharmaceutical wastewater. In this project, main emphasis is placed on the understanding the action mechanism between unsaturated iron particles, organic ligands and iron NPs of catalysts, the stability of catalysts and the degradation pathways. Results concerning the characterization of active sites are also studied in detail with respect to explore the factors determining the reaction rate and investigate the reasonable catalytic mechanism.

异相Fenton催化技术是处理高浓度、难生物降解废水的有效方法，如何使其在宽pH条件下高效稳定的发生反应是研究的热点和难点。本项目首次构筑基于介孔铁基MOFs的新型异相Fenton催化剂。该催化剂骨架中特有的高密度不饱和金属铁和易功能化的有机配体使其具有高活性和稳定性。并设计以介孔铁基MOFs为载体,利用其高比表面积和可调孔道组装第二活性组分纳米零价铁，产生协同束缚效应进一步提高催化性能；同时借鉴有机铁络合物中性条件下可发生Fenton反应的特性，通过对有机配体的优化和修饰，实现在宽pH值范围内发生Fenton反应。且巧妙利用介孔孔道对大分子污染物的高效吸附，将新型催化剂有针对性地应用于pH变化大的大分子制药废水的处理，考察污染物降解性能，解析中间产物，揭示不饱和金属铁、有机配体和纳米零价铁之间的协同作用机制，识别影响催化性能的关键因素，探讨构效关系，阐明降解污染物的规律特点和反应机理。

异相Fenton催化技术是处理高浓度、难生物降解废水的有效方法。但如何使其在宽pH值范围内高效、稳定的工作是环保领域研究的难点和热点。本项目以构筑基于铁基MOFs的新型异相Fenton催化剂，具体通过具有高表面积、规则网状结构的铁基金属有机骨架MIL-100(Fe)为载体，通过负载第二活性组分，构筑了负载型铁基金属有机骨架异相Fenton催化剂，用于对特征性污染物的去除，考察污染物的降解性能，揭示催化降解的协同作用机制，阐述构效关系，阐释污染物的降解规律和反应机理。铁基MOFs系列催化剂的设计与构筑从两个方面入手，一是通过将第二活性组分FeII负载到吸附性能优异的MIL-100(Fe)骨架上得到负载型催化剂FeII@MIL-100(Fe)，二是将MIL-100(Fe)与磁性物质Fe3O4复合到一起构筑核壳型催化剂Fe3O4@ MIL-100(Fe)。这两种构筑方式均能有效地将第二组分的优点与MIL-100(Fe)自身的催化活性和吸附优势进行功能化组装，进而提高负载型催化剂的催化活性，高效地降解水环境中的污染物。具体的研究内容为: (1) 构筑了一种具有高比表面积和高催化活性的铁基金属有机骨架异相Fenton催化剂FeII@MIL-100(Fe)。FeII@MIL-100(Fe)拥有较高的比表面积达1228 m2/g, 拥有高的Fenton催化活性。FeII@MIL-100(Fe)结构中FeII和FeIII组分之间的协同作用极大地加强了羟基自由基的产率、催化剂表面的氧化还原性能。铁基金属有机骨架MIL-100(Fe)的催化活性在3~8的宽pH值范围内比较稳定，即使在酸性条件，铁离子溶出也能控制在相对较低的水平。(2) 采用层层组装法构筑了不同壳层厚度的核壳型铁基金属有机骨架Fe3O4@MIL-100(Fe)并首次应用于异相光Fenton催化降解有机污染物。核壳型催化剂体现了壳层MIL-100(Fe)优异的吸附性能可迅速将催化剂吸附到壳层表面。MIL-100(Fe)还具有强的光催化性能，当同时引入核部Fe3O4和H2O2时，光生电子和H2O2反应产生∙OH，而光生空穴则转移到核Fe3O4中，这极大地提高了光生电子和空穴的分离度，不仅可以增强MOFs材料的光催化性能，还能提高∙OH的产生量。